Die bonder and methods of using the same

ABSTRACT

A method includes bringing into contact respective first sides of a plurality of dies and a die attach film on a major surface of a carrier wafer, and simultaneously heating portions of the die attach film contacting the plurality of dies in order to simultaneously bond the plurality of dies to the die attach film.

PRIORITY CLAIM AND CROSS-REFERENCE

This application claims the benefit of the following provisionally filedU.S. Patent application: Application Ser. No. 62/096,979 filed Dec. 26,2014, and entitled “Die Bonder and Methods of Using the Same,” whichapplication is hereby incorporated herein by reference.

BACKGROUND

With the evolving of semiconductor technologies, semiconductorchips/dies are becoming increasingly smaller. In the meantime, morefunctions need to be integrated into the semiconductor dies.Accordingly, the semiconductor dies need to have increasingly greaternumbers of I/O pads packed into smaller areas, and the density of theI/O pads rises quickly over time. As a result, the packaging of thesemiconductor dies becomes more difficult, which adversely affects theyield of the packaging.

Conventional package technologies can be divided into two categories. Inthe first category, dies on a wafer are packaged before they are sawed.This packaging technology has some advantageous features, such as agreater throughput and a lower cost. Further, less underfill or moldingcompound is needed. However, this packaging technology also suffers fromdrawbacks. Since the sizes of the dies are becoming increasinglysmaller, and the respective packages can only be fan-in type packages,in which the I/O pads of each die are limited to a region directly overthe surface of the respective die. With the limited areas of the dies,the number of the I/O pads is limited due to the limitation of the pitchof the I/O pads. If the pitch of the pads is to be decreased, solderbridges may occur. Additionally, under the fixed ball-size requirement,solder balls must have a certain size, which in turn limits the numberof solder balls that can be packed on the surface of a die.

In the other category of packaging, dies are sawed from wafers beforethey are packaged. An advantageous feature of this packaging technologyis the possibility of forming fan-out packages, which means the I/O padson a die can be redistributed to a greater area than the die, and hencethe number of I/O pads packed on the surfaces of the dies can beincreased. Another advantageous feature of this packaging technology isthat “known-good-dies” are packaged, and defective dies are discarded,and hence cost and effort are not wasted on the defective dies.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 5 illustrate the cross-sectional views of intermediatestages in the bonding of dies to a die attach film in accordance withsome embodiments;

FIGS. 6 and 7 illustrate the cross-sectional views of intermediatestages in the formation of fan-out packages from the dies bonded to thedie attach film in accordance with some embodiments;

FIG. 8 illustrates a bonder design in accordance with some embodiments;

FIGS. 9 through 12 illustrate portions of the bonder and the operationin accordance with some embodiments;

FIGS. 13 through 16 illustrate the cross-sectional views of intermediatestages in the bonding of dies to a die attach film in accordance withsome embodiments, wherein a vacuum die holder is used as a temporary dieholder;

FIGS. 17 through 19 illustrate the cross-sectional views of intermediatestages in the bonding of dies to a die attach film in accordance withsome embodiments, wherein an adhesive tape is used as a temporary dieholder; and

FIG. 20 illustrates a process flow in the formation of a fan-out packagein accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A bonder design and the methods of using the bonder to bond dies ontoDie Attach Films (DAFs) are provided in accordance with variousexemplary embodiments. The intermediate stages of forming a packagebased on the dies bonded onto the DAFs are illustrated. The variationsof the embodiments are discussed. Throughout the various views andillustrative embodiments, like reference numbers are used to designatelike elements.

FIGS. 1 through 7 illustrate the cross-sectional views of intermediatestages in the formation of a fan-out package in accordance with someembodiments. The steps shown in FIGS. 1 through 7 are also illustratedschematically in the process flow 200 shown in FIG. 20. In thesubsequent discussion, the process steps shown in FIGS. 1 through 7 arediscussed referring to the process steps in FIG. 20.

Referring to FIG. 1, sawed wafer 24 is attached to dicing tape 20, whichis used to adhere to the discrete dies 22 in wafer 24. In accordancewith some embodiments of the present disclosure, dies 22 includeintegrated circuit devices such as transistors, diodes, resistors,capacitors (not shown), and/or the like. Dies 22 may include asemiconductor substrate (not marked) such as a silicon substrate, aIII-V compound semiconductor substrate, a germanium substrate, a silicongermanium substrate, or the like. It is appreciated that although dies22 are illustrated as separated far away from each other for clarity,dies 22 are actually closely located from each other, with kervesgenerated in the die-sawing process to separate dies 22 from each other.Furthermore, wafer 24 is a round wafer viewed from top, as shown in FIG.8.

Referring to FIG. 2A, dies 22 are picked up from dicing tape 20 andtransferred over carrier wafer 28 and the overlying DAF 30. Therespective step is illustrated as step 202 in the process flow 200 shownin FIG. 20. In accordance with some embodiments of the presentdisclosure, carrier wafer 28 is a glass carrier wafer, or may be formedof other transparent materials, which may be transparent to, for exampleUltra Violet (UV) light. Other material such as organic materials,ceramics, or the like, may also be used. DAF 30 is attached to carrierwafer 28, and may be formed/attached, for example, through lamination orcoating. DAF 30 has the characteristic that when heated, becomes stickyenough, and hence dies 22 may be adhered thereon, as will be discussedin subsequent paragraphs. Carrier wafer 28 and DAF 30 may have a topview of a typical wafer, for example, with a round top-view shape. Insome exemplary embodiments, DAF 30 is formed of a Light To HeatConversion (LTHC) material.

As shown in FIG. 2A, die 22 is picked up by pickup head 32A, which maybe a vacuum head that is capable of picking up die 22 through vacuum. Inaccordance with some embodiments of the present disclosure, vacuum head32A is not heated (and may not be cooled either). Accordingly, vacuumhead 32A has a temperature equal to the ambient temperature of thesurrounding environment (such as the internal environment of bonder 120as illustrated in FIG. 8) in which wafer 24 is located. For example, thetemperature of vacuum head 32A may be equal to room temperature, whichmay be in the range between about 18° C. and about 25° C. Furthermore,the temperature of vacuum head 32A may be close to the temperature ofwafer 24, for example, with the difference between the temperatures ofvacuum head 32A and wafer 24 being smaller than about 5° C.

In accordance with some embodiments of the present disclosure, thepicked up die 22 is handed off to placement head 32B, which is also ableto suck up die 22 through vacuum. In accordance with some embodiments ofthe present disclosure, placement head 32B is heated to a temperaturehigher than the ambient temperature of the environment in which wafer 24is located. For example, the temperature of placement head 32B may behigher than the temperatures of wafer 24 and the ambient temperature bya difference greater than about 25 degrees. In accordance with someembodiments of the present disclosure, the temperature of placement head32B is in the range between about 50° C. and about 200° c.

In accordance with alternative embodiments of the present disclosure,placement head 32B is not heated (and may not be cooled either).Accordingly, the temperature of placement head 32B is equal to theambient temperature of the environment in which wafer 24 is located, andmay be close to the temperature of wafer 24, for example, with thedifference between the temperatures of vacuum head 32A and wafer 24being smaller than about 5° C.

Placement head 32B is used to place die 22 onto DAF 30, as shown in FIG.2A. In accordance with some embodiments, a low pressure is applied topress die 22 against DAF 30. In accordance with alternative embodiments,die 22 is placed on DAF 30 with no pressure applied. The position of die22 is determined through an alignment process, and hence die 22 isplaced accurately to the desirable position. Throughout the description,pickup head 32A and placement head 32B are collectively referred to aspick and place head(s) 32.

FIG. 2B illustrates the pick and place of die 22 in accordance withalternative embodiments, in which a same pick and place head 32 is usedto pick up die 22 from dicing tape 20 and place die 22 onto DAF 30.Accordingly, no hand off is conducted during the transferring of die 22from dicing tape 20 to DAF 30. In these embodiments, pick and place head32 is not heated. For example, pick and place head 32 may have the roomtemperature.

In accordance with some embodiments of the present disclosure, die 22 isplaced facing up. For example, electrical connectors 23 areschematically illustrated, with the side with the electrical connectors23 being the front side, which faces up. Electrical connectors 23 may bemetal pillars, solder regions, metal pads, or other conductive features.The opposite side (the side in contact with DAF 30) is the backside ofdie 22. In some embodiments, the backside of die 22 is also the backsideof the semiconductor substrate (not shown) in die 22, on whichintegrated circuit devices are formed. Accordingly, in some embodiments,the backside of the semiconductor substrate is in physical contact withDAF 30.

Next, referring to FIG. 3, the process steps as shown in FIGS. 1 and 2A(or FIGS. 1 and 2B) are repeated, and more dies 22 are transferred ontoDAF 30. The process is continued until all locations over DAF 30 thatare intended to be placed with dies are placed. In the placement of dies22, dies 22 are placed with or without pressure applied to press dies 22against DAF 30. Furthermore, during and between the pick and place ofdies 22, there is no additional heating process applied onto carrierwafer 28, DAF 30, and dies 22. Accordingly, after all dies 22 areplaced, dies 22 are placed over, but are not adhered to, DAF 30.

FIGS. 4 and 5 illustrate the process for heating dies 22 and pressingdies 22 against DAF 30, so that dies 22 are adhered to DAF 30 by asticking force. The respective step is illustrated as step 204 in theprocess flow 200 shown in FIG. 20. Referring to FIG. 4, hot plate 34 ismoved to the top of dies 22. Hot plate 34 may be formed of a metal or ametal alloy including copper, aluminum, stainless steel, nickel, or thelike. Hot plate 34 may also be formed of other materials such asceramic. The bottom surface of hot plate 34 is coplanar, and may be thesurface of the same material such as the same metal or metal alloy.Heating unit 36 is schematically illustrated. In accordance with someembodiments of the present disclosure, heating unit 36 comprises a coilthat when conducted with an electrical current, heats hot plate 34 to adesirable temperature. Heating unit 36 may be embedded in hot plate 34.Alternatively, heating unit 36 may be placed over hot plate 34. Inaccordance with some embodiments, the temperature of hot plate 34 isincreased to higher than about 50° C., and may be in the range betweenabout 50° C. and about 200° C.

Next, referring to FIG. 5, hot plate 34 is brought into contact withdies 22. Dies 22 are thus heated by hot plate 34. In addition, apressure (represented by arrows) is applied to press dies 22 against DAF30. Heat is conducted through dies 22 and reaches the bottom surfaces ofdies 22, which are in contact with DAF 30, and hence the portions of DAFfilm 30 directly underlying dies 22 are heated and become adhesive. Thebottom surfaces of dies 22 may be heated to a temperature higher thanabout 50° C. The temperature may also be in the range between about 50°C. and about 200° C.

Hot plate 34 is pressed against dies 22 for a certain period of time,for example, longer than about 0.5 seconds, or in the range betweenabout 0.5 seconds and about 2 seconds. The temperature and the period oftime are related to various factors including, and not limited to, thethickness of dies 22, the material and structure of dies 22, thematerial of DAF 30, and the like. The optimum temperature and theoptimum period of time are selected to ensure that dies 22 are reliablyadhered to DAF 30. Throughout the description, the adhering of dies 22to DAF 30 is referred to as the bonding of dies 22 to DAF 30, and therespective heating and pressing process are referred to as a bondingprocess.

After dies 22 are bonded to DAF 30, hot plate 34 is lifted up and movedaway. The respective step is illustrated as step 206 in the process flow200 shown in FIG. 20. In accordance with some embodiments of the presentdisclosure, the above-discussed bonding of dies 22 includes two phases.In the first phase, dies 22 are placed onto DAF 30, wherein no bondingprocess is performed to bond dies 22 to DAF 30, until all dies 22 areplaced. In the second phase, a hot plate is used to simultaneously bondall dies 22 to DAF 30 through the heating and the pressing of dies 22simultaneously. Accordingly, a single bonding process is shared by alldies 22 regardless of the count of dies 22 on carrier wafer 28. Thethroughput of the bonding process is thus very high. As a comparison, inconventional bonding process, each of dies is picked up and placed onthe respective DAF, followed by a heating and pressing process, untilthe die is bonded to the DAF. Therefore, the bonding time isproportional to the count of the dies. For example, assuming more than athousand dies are bonded, with the bonding of each die taking onesecond, the total time for bonding all dies will be longer than 1,000seconds.

In addition, with hot plate 34 having a coplanar bottom surface, afterthe bonding of dies 22 onto DAF 30, the top surfaces of dies 22 arehighly coplanar with each other, which results in the reduction in theprocess difficulty in the formation of the subsequently performedfan-out process.

In a subsequent step, as shown in FIG. 6, molding material 41, which maybe a molding compound (such as a polymer) is used to mold dies 22therein. The respective step is illustrated as step 208 in the processflow 200 shown in FIG. 20. A planarization step such as a ChemicalMechanical Polish (CMP) is then performed to planarize the top surfaceof molding material 41 to be coplanar with the top surfaces of dies 22.Furthermore, electrical connectors 23 of dies 22 are exposed after theplanarization step.

FIG. 6 further illustrates the formation of dielectric layers 38,Redistribution Lines (RDLs) 40, and electrical connectors 42. Therespective step is also illustrated as step 208 in the process flow 200shown in FIG. 20. In accordance with some embodiments of the presentdisclosure, dielectric layers 38 are formed of a polymer, which may alsobe a photo-sensitive material such as polybenzoxazole (PBO), polyimide,or the like, that can be easily patterned using a photo lithographyprocess. In accordance with alternative embodiments, dielectric layers38 are formed of a nitride such as silicon nitride, an oxide such assilicon oxide, PhosphoSilicate Glass (PSG), BoroSilicate Glass (BSG),Boron-doped PhosphoSilicate Glass (BPSG), or the like. RDLs 40 may beformed of aluminum, copper, aluminum copper, nickel, gold, palladium, orthe like. Electrical connectors 42 may include solder regions, metalpillars capped with solder layers, or the like. RDLs 40 are electricallycoupled to electrical connectors 23, which are further electricallycoupled to the integrated circuit devices in dies 22.

The structure shown in FIG. 6 is referred to as a fan-out structure,wherein RDLs 40 and electrical connectors 42 extend beyond the footprintof the respective dies 22. Alternatively stated, RDLs 40 and electricalconnectors 42 extend to regions beyond the edges of the respective dies22, so that electrical connectors 42 may have larger pitches thanelectrical connectors 23. The bonding of the respective packageincluding die 22 is thus easier than the direct bonding of dies 22,whose electrical connectors have smaller pitches. Throughout thedescription, dies 22, molding material 41, and the overlying dielectriclayers 38, RDLs 40, and electrical connectors 42 are collectivelyreferred to as composite wafer 100.

FIG. 7 illustrates the adhering of dicing tape 44 to electricalconnectors 42. DAF 30 and carrier wafer 28 as shown in FIG. 6 are thenreleased from dies 22, for example, by projecting a light (not shown) onDAF 30, so that the heat of the light decomposes DAF 30, and hence DAF30 and carrier wafer 28 are no longer adhered to carrier wafer 28. Therespective step is illustrated as step 210 in the process flow 200 shownin FIG. 20. Subsequently, composite wafer 100 is sawed apart in adie-saw process to form a plurality of fan-out packages 102. Therespective step is illustrated as step 212 in the process flow 200 shownin FIG. 20. Each of the fan-out packages 102 includes one of dies 22 andthe overlying RDLs.

In accordance with some embodiments of the present disclosure, thebonding process as shown in FIGS. 2A, 2B, and 3-5 may be performed usingbonder 120 as shown in FIG. 8. Referring to FIG. 8, bonder 120 includeswafer loading port 122, which is configured to load wafer 24 into bonder120. For example, wafer 24 may be stored in and transported using wafercassette 124, which may store a plurality of sawed wafers 24. Afterwafer cassette 124 is connected to bonder 120, wafer 24 is loaded intobonder 120 through loading port 122.

Bonder 120 further includes carrier loading port 126, which isconfigured to load carrier wafer 28 and DAF 30 into bonder 120. Pick andplace unit 132 is configured to pickup dies 22 (FIGS. 2A and 2B) andplace dies 22 onto carrier wafer 28. The pick and place head 32/32A/32Bas shown in FIGS. 2A and 2B are parts of the pick and place unit 130. InFIG. 8, the dashed box 32 is illustrated to represent that pick andplace head 32 picks up die 22 from wafer 24, and the solid box 32 isillustrated to represent the placement of die 22 onto carrier wafer28/DAF 30. After all usable dies 22 on wafer 24 is placed on carrierwafer 28, the underlying tape 20 is unloaded, and another wafer 24 isloaded in.

Alignment unit 134 is disposed in bonder 120, and is used for aligningdies 22, so that dies 22 may be accurately placed to their intendedpositions. FIG. 9 illustrates a simplified view of portions of bonder120, wherein alignment element 134 and the transferring of dies 22 areillustrated. Alignment unit 134 is configured to find alignment marks(not shown) in dies 22, and pick and place unit 130 then moves dies 22according to the results of the alignment to place dies 22 on carrierwafer 38/DAF 30.

Referring back to FIG. 8, in accordance with some embodiments of thepresent disclosure, hot plate 34 is disposed inside bonder 120, and isconnected to transfer arm unit 136, which is configured to move hotplate 34 toward and away from carrier wafer 28 and the overlying placeddies 22. In accordance with some embodiments of the present disclosure,transfer arm unit 136 includes swivel arm 138 configured to swivel hotplate 34 back and forth between its illustrated position and carrierwafer 28. FIG. 10 illustrates a simplified view of portions of bonder120, wherein the swivel of swivel arm 138 is illustrated using an arrow.When dies 22 are being placed onto DAF 30, hot plate 34 is located atits illustrated position in FIG. 10. When the placement of dies 22 isfinished, swivel arm 138 is swiveled to move hot plate 34 over dies 22,so that hot plate 34 may be brought into contact with dies 22, and hencedies 22 is bonded to DAF 30. After the bonding, swivel arm 138 isswiveled to move hot plate 34 back to the illustrated position in FIG.8. FIG. 11 illustrates a cross-sectional view of the bonding process,wherein swivel arm 138 and hot plate 34 are moved from the locationillustrated using dashed patterns to the location illustrated usingsolid patterns, so that dies 22 are bonded to DAF 30/carrier wafer 28.

In alternative embodiments, bonder 120 is configured to perform the taskshown in FIGS. 13 through 19, for example, with hot plate 34 being avacuum head 50 configured to pick up and heat carrier wafer 28, as shownin FIGS. 15 and 18. The details will be discussed in subsequentparagraphs. In these embodiments, dies 22 will be transferred to vacuumdie holder 46 (FIG. 13) or adhesive tape 52 (FIG. 17).

In accordance with some embodiments of the present disclosure, heatingunit 36 is embedded in hot plate 34, as also shown in FIG. 4. In theseembodiments, hot plate 34 is heated by heating unit 36, which may heathot plate 34 during, and between, the bonding processes. In alternativeembodiments, heating unit 36 (FIG. 8) is outside of hot plate 34, andhot plate 34 is placed on heating unit 36 to be heated to a desirabletemperature. In the bonding process, hot plate 34 is moved to dies 22 tobond dies 22, during which heating unit 36 remains not moved, and henceduring the bonding process, hot plate 34 is not heated by heating unit36. After the heating process, hot plate 34 moves back to be heated byheating unit 36.

Referring back to FIG. 8, after the bonding, the bonded dies 22 and therespective underlying DAF 30 and carrier wafer 28 are unloaded out ofbonder 120, for example, through loading port 126.

In accordance with alternative embodiments of the present disclosure,after all dies 22 are placed onto DAF 30, but before the bonding throughheating and pressing, dies 22 and the underlying DAF 30 and carrierwafer 28 are unloaded out of bonder 120. The bonding, which includesheating and pressing, of dies 22 to DAF 30 is performed by an externalhot plate 34 outside of bonder 120.

As shown in FIG. 8, bonder 120 includes central control unit 142, whichis connected to, and is configured to control and coordinate thefunctions of, all units of bonder 120 including wafer loading port 122,carrier loading port 126, transfer arm unit 136, etc.

In accordance with some embodiments of the present disclosure, as shownin FIG. 12, a multi-head pick and place unit 132 may be used to pick upmultiple dies 22 simultaneously. Multi-head pick and place unit 132includes a plurality of pick and place head 32, which may be vacuumheads. Each of the pick and place head 32 is configured to pick andplace one of dies 22. Arrows 140 represent that multi-head pick andplace unit 132 moves as an integrated unit to alignment unit 134, andthen places dies 22 onto DAF 30/carrier wafer 28. Advantageously, sincethe relative positions of dies 22 picked up by multi-head pick and placeunit 132 can be controlled, the alignment may be performed on a singleone, and not all of, the picked up dies 22. This may significantlyimprove the throughput. Alternatively, the alignment is performed on allof the dies 22 that are picked up by pick and place unit 132.

FIGS. 13 through 16 illustrate cross-sectional views of intermediatestages in the formation of a bonding process in accordance withalternative embodiments. Unless specified otherwise, the materials andthe formation methods of the components in these embodiments areessentially the same as the like components, which are denoted by likereference numerals in the embodiments shown in FIGS. 1 through 8. Thedetails regarding the process and the materials of the components shownin FIGS. 13 through 16 (and FIGS. 17 through 19) may thus be found inthe discussion of the embodiments shown in FIGS. 1 through 12.

Referring to FIG. 13, dies 22 are transferred from sawed wafer 24 tovacuum die holder 46, which acts as a temporary die holder. Vacuum dieholder 46 may be formed of a metal such as aluminum, copper, stainlesssteel, or the like, or another material such as ceramic. A plurality ofthrough-holes 48 is disposed to penetrate through the bottom panel ofvacuum die holder 46. Each of dies 22 may be aligned to one or aplurality of holes 48 after being placed on vacuum die holder 46.

Referring to FIG. 14, through-holes 48 may be connected to pump 144.After all dies 22 are placed, the internal spaces in through-holes 48are vacuumed by pump 144 to generate a suction force, and hence dies 22are fixed to vacuum die holder 46 by the suction force. In theseembodiments, dies 22 have their front surface facing vacuum die holder46.

Next, also referring to FIG. 14, vacuum head 50 is used to pick upcarrier wafer 28 and DAF 30, with DAF 30 facing dies 22. Vacuum head 50is also a hot plate that heats carrier wafer 28 and DAF 30, so that DAF30 is heated to a desirable temperature, which may be higher than about50° C., and may be in the range between about 50° C. and about 200° C.Dies 22 may or may not be heated by vacuum die holder 46. DAF 30 is thenbrought into contact with the back surfaces of dies 22, as shown in FIG.15. A pressing force may also be applied, for example, for a period oftime between about 0.5 seconds and about 2 seconds, so that dies 22 arebonded to DAF 30.

Next, the vacuuming of through-holes 48 is stopped, so that dies 22 arereleased from vacuum die holder 46. Vacuum head 50 may then pick upcarrier wafer 28, DAF 30, and the dies 22 attached thereon, as shown inFIG. 16. In subsequent steps, the process shown in FIGS. 6 and 7 may beperformed.

FIGS. 17 through 19 illustrate the cross-sectional views of intermediatestages in the bonding of dies in accordance with yet other embodiments.Referring to FIG. 17, dies 22 are transferred from sawed wafer 24 toadhesive film 52 (which may be a UV tape), which is adhered to temporarysubstrate 54. Temporary substrate 54 may also be a carrier wafer formedof, for example, glass. The front sides of dies 22 are adhered to UVtape 52. The transferring of dies 22 may be conducted by pick and placehead 32, which is not heated in accordance with some embodiments of thepresent disclosure.

Next, referring to FIG. 18, vacuum head 50 is used to pick up carrierwafer 28 and DAF 30, with DAF 30 facing dies 22. Vacuum head 50 is alsoa hot plate that heats carrier wafer 28 and DAF 30, so that DAF 30 isheated to a desirable temperature, which may be higher than about 50°C., and may be in the range between about 50° C. and about 200° C. DAF30 is brought into contact with the back surfaces of dies 22. A pressingforce is applied, for example, for a period of time between about 0.5seconds and about 2 seconds, so that dies 22 are bonded to DAF 30.

Next, adhesive tape 52 and carrier wafer 54 are removed from dies 22,for example, by projecting a UV light on adhesive tape 52, so thatadhesive tape 52 loses adhesion, and dies 22 are released from adhesivetape 52. Vacuum head 50 may then pick up carrier wafer 28, DAF 30, andthe dies 22 attached thereon. In subsequent steps, the process shown inFIGS. 6 and 7 may be performed.

The embodiments of the present disclosure have some advantageousfeatures. By bonding the dies to the DAF simultaneously, the bondingtime is significantly reduced comparing to picking and placing dies, andbonding each of the dies to the DAF separately. The throughput of thebonding process is thus significantly improved.

In accordance with some embodiments of the present disclosure, a methodincludes bringing into contact respective first sides of a plurality ofdies and a die attach film on a major surface of a carrier wafer, andsimultaneously heating portions of the die attach film contacting theplurality of dies in order to simultaneously bond the plurality of diesto the die attach film.

In accordance with alternative embodiments of the present disclosure, amethod includes placing a plurality of dies to have first surfaces ofthe plurality of dies coplanar with each other, and heating theplurality of dies or a die attach film using a hot plate, with the hotplate being pressed against the plurality of dies, so that second sidesof the plurality of dies are bonded to the die attach film. After thesecond sides of the plurality of dies are bonded to the die attach film,the hot plate is moved away from the plurality of dies and the dieattach film.

In accordance with yet alternative embodiments of the presentdisclosure, an apparatus for bonding a plurality of dies to a die attachfilm includes a pick and place unit for placing the plurality of dies,and a heating unit configured to simultaneously bond the plurality ofdies to the die attach film by heating portions of the die attach filmin contact with the plurality of dies simultaneously.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: bringing into contact respective first sides of a plurality of dies with a die attach film, wherein the die attach film is on a major surface of a carrier wafer; heating portions of the die attach film in contact with the plurality of dies to cause the plurality of dies to stick to the die attach film, wherein the plurality of dies starts to be heated at a same time; after the plurality of dies is bonded to the carrier wafer, molding the plurality of dies with a molding material; forming redistribution lines to electrically couple to the plurality of dies; and releasing the plurality of dies, the molding material, and the redistribution lines from the die attach film.
 2. The method of claim 1, wherein the heating comprises simultaneously heating second sides of the plurality of dies to conduct heat to the portions of the die attach film.
 3. The method of claim 1, wherein the heating comprises heating an entirety of the die attach film through heating the carrier wafer.
 4. The method of claim 1 further comprising, before the bringing into contact, placing the plurality of dies onto the die attach film, with back surfaces of the plurality of dies in contact with the die attach film.
 5. The method of claim 1 further comprising: before the bringing into contact, placing the plurality of dies onto a vacuum die holder; fixing the plurality of dies to the vacuum die holder through vacuuming, wherein the die attach film is brought into contact with the plurality of dies that is fixed to the vacuum die holder; and releasing the plurality of dies and the die attach film from the vacuum die holder.
 6. The method of claim 1 further comprising: before the bringing into contact, placing the plurality of dies onto an adhesive tape, wherein the die attach film is brought into contact with the plurality of dies that is fixed to the adhesive tape; and releasing the plurality of dies and the die attach film from the adhesive tape.
 7. A method comprising: placing a plurality of dies to have first surfaces of the plurality of dies coplanar with each other, wherein the plurality of dies is placed sequentially; after the plurality of dies is placed, heating the plurality of dies or a die attach film using a hot plate, with the hot plate being pressed against the plurality of dies, so that second sides of the plurality of dies are adhered to the die attach film through a gluing force; and after the second sides of the plurality of dies are bonded to the die attach film, moving the hot plate away from the plurality of dies and the die attach film.
 8. The method of claim 7, wherein in the heating, the hot plate is in physical contact with the plurality of dies.
 9. The method of claim 7, wherein in the heating, the hot plate is in physical contact with a carrier wafer, with the die attach film being between, and in contact with, the carrier wafer and the plurality of dies.
 10. The method of claim 7 further comprising: swiveling the hot plate to heat the plurality of dies; and after the plurality of dies is bonded to the die attach film, swiveling the hot plate away from the plurality of dies.
 11. The method of claim 7, wherein the placing the plurality of dies comprises placing the plurality of dies directly on the die attach film, with surfaces of the second sides of the plurality of dies being in physical contact with the die attach film, and the method further comprises: encapsulating the plurality of dies in an encapsulating material, wherein the encapsulating material is in physical contact with the die attach film; and forming redistribution lines over the encapsulating material and the plurality of dies, wherein the redistribution lines are electrically connected to the plurality of dies.
 12. The method of claim 7, wherein the placing the plurality of dies comprises: placing the plurality of dies on a vacuum die holder; and generating a vacuum to fix the plurality of dies onto the vacuum die holder.
 13. The method of claim 7, wherein the placing the plurality of dies comprises: placing the plurality of dies on an adhesive tape, wherein the adhesive tape and the die attach film are on opposite sides of the plurality of dies; and removing the adhesive tape from the plurality of dies, with the die attach film being bonded to the plurality of dies after the adhesive tape is removed.
 14. A method comprising: placing a plurality of dies onto a die attach film; contacting a hot plate with top surfaces of the plurality of dies; heating the plurality of dies using the hot plate, wherein heat is conducted from the hot plate to the die attach film, so that the plurality of dies is bonded to the die attach film; with the plurality of dies being bonded to the die attach film, encapsulating the plurality of dies in an encapsulating material, wherein the encapsulating material is in contact with top surfaces of portions of the die attach film; forming redistribution lines over the encapsulating material and the plurality of dies, wherein the redistribution lines are electrically connected to the plurality of dies; and performing a die-saw on the die attach film and the encapsulating material to form a plurality of packages, wherein each of the packages comprises one of the plurality of dies.
 15. The method of claim 14, wherein in the heating, the hot plate is in physical contact with the plurality of dies, and a surface of the hot plate in contact with the plurality of dies is a planar surface.
 16. The method of claim 14, wherein the plurality of dies is placed one by one onto the die attach film, and during a period of time the plurality of dies is placed, the placed ones of the plurality of dies are not heated.
 17. The method of claim 14, wherein the placing the plurality of dies comprises: placing the plurality of dies on a vacuum die holder; and generating a vacuum to fix the plurality of dies onto the vacuum die holder, wherein the hot plate is in contact with the plurality of dies after the vacuum is generated.
 18. The method of claim 14, wherein the placing the plurality of dies comprises: placing the plurality of dies onto an adhesive tape, wherein the adhesive tape and the die attach film are on opposite sides of the plurality of dies; and removing the adhesive tape from the plurality of dies, with the die attach film being bonded to the plurality of dies after the adhesive tape is removed.
 19. The method of claim 14, wherein in each of the packages, the piece of the die attach film is in contact with a bottom surface of a respective die and a bottom surface of the encapsulating material.
 20. The method of claim 7, wherein the heating results in the die attach film to be adhesive. 